This application relates to specific compound detection systems, and more particularly to systems incorporating liquid chromatography and specific gas detection techniques.
In general, prior art specific compound detection systems incorporating liquid chromatography and specific gas detection techniques face severe limitations in sensitivity and specificity due to the presence of trace contaminants and sample solvent which interfere with the detection of the specific gas. Accordingly, much care has been required in the selection of appropriate solvents and, of course, for particular cases, suitable solvents are not available. Furthermore, with respect to contaminants, elimination techniques have been of limited effectiveness. The above problems have been particularly evident in the detection of N-nitros compounds.
N-Nitroso compounds are among the most carcinogenic compounds presently known. A single part per million dose may suffice to produce tumors. These compounds have been found in trace quantities in many materials which are taken internally by humans, such as artificial food additives and tabacco smoke. In addition, they may be formed in vivo by internally taking the chemical precursors. In the continuing research into tumor producing substances, N-nitroso compounds are compounds which require study and for which tolerable levels of human consumption need to be determined. As of yet, such levels have not been adequately determined. This is due, at least in part, to the difficulty in measuring the quantity of N-nitrosoamine compounds in particular samples.
One prior method of N-nitroso compound measurement is to heat the N-nitroso compound with hydrogen to convert the nitrogen in the N-nitroso compound to ammonia. The resulting ammonia may then be detected. The major disadvantage of this method is amines and amino acids and other nitrogen fragments are also converted to ammonia and are difficult to distinguish from the ammonia produced by the N-nitroso compounds. This problem may be partly, but only partly, overcome by prior separation on a gas chromatograph column. Even then, identification of the ammonia resulting from converted N-nitroso compounds must be confirmed by high sensitivity mass spectrometry. The results of such a process are very difficult and time consuming to obtain.
Another method which has been tried involves dissolving a sample in a solvent to which nitric oxide dyes are added. Exposure to ultraviolet light produces a color change. The color change was measured to provide a reading of N-nitrosoamine content. The method provided very little success. One reason is that other materials which commonly occur in samples also produce color change and thereby erroneous readings. One such other material is furfural.